1. Field
One embodiment of the invention relates to an information storage medium, an information recording method, and an information reproducing method.
2. Description of the Related Art
It has been a long time since information recording media capable of recording and reproducing information using laser light, that is to say, optical discs were put to practical use. For example, several hours of images of a normal quality can be recorded on an optical disc of a DVD (digital versatile disc) standard which is 12 cm in diameter. In a read-only optical disc, images and contents can be recorded in a short time by pressing or molding. In addition, a land pre-pit and a groove track (pre-groove) are formed in a type of optical disc which permits recording (write-once) or erasing (re-recordable) of information.
Jpn. Pat. Appln. KOKAI Publication No. 2001-266362 has shown that, when a new recording mark is to be recorded in an information storage medium having a pre-groove and a land pre-pit, (a) a large detection signal is obtained from the land pre-pit to ensure the reliability in reproduction from address information recorded in the land pre-pit, and (b) a large off-track detection signal is obtained from the pre-groove to ensure high tracking stability during the formation of the recording mark.
Hitherto, in the optical discs of the DVD standard, the identification of a disc has been carried out using a book type recorded in higher four bits of a byte position BP0 of a physical format information zone in a lead-in area. The book type indicates a predetermined code allocated to each standard document of the DVD forum. A part version is recorded in lower four bits of the byte position BP0. The part version indicates not the digit of a version number itself but a predetermined code allocated to each version of a standard document of the DVD forum. For example, 0000b is allocated to a version 0.9 (for testing), 0001b is allocated to a version 1.0x, 0100b is allocated to a version 1.9 (for testing), 0101b is allocated to a version 2.0×, and 0110b is allocated to a version 2.1×, and the rest are reserved.
In recent years, studies have been carried out on a new standard for recording encrypted contents on a disc. There has been a desire that a recordable disc (write-once, re-recordable or rewritable disc) in which encrypted contents are recorded in accordance with this standard be played back not by a device which has recorded the encrypted contents but by other players. Thus, it is necessary for the player to recognize the recorded disc as a read-only DVD-ROM even if the disc is a recordable disc. The reason is that, originally, there has been a rule which forbids encrypted contents to be reproduced when the encrypted contents are recorded on the recording medium in view of security, so that there are a large number of devices designed to be unable to reproduce the encrypted contents if the book type is not the DVD-ROM.
However, as there are increasing needs for downloading encrypted contents, recording the contents on a disc and then reproducing the contents from the disc due to the recent development of networks, the book type has to be the DVD-ROM.